1. Field of the Invention
The present invention relates to vehicle roof support structures.
2. Background Art
Vehicle roofs are supported by pillars that are generally referred to as A, B, and C pillars. Other parts of the support structure of a vehicle roof include roof rails that extend fore and aft on opposite lateral sides of the vehicle and roof bows that extend transversely between the roof rails. Vehicle roofs are supported on the pillars, roof rails and roof bows.
Roof rails and pillars of conventional construction generally include several sheet metal panels that are formed in a stamping process and assembled together with resistance, or spot welds. Conventional roof construction processes are labor intensive. Roofs formed by conventional construction techniques provide sufficient strength to meet the current standard FMVSS216 for “Roof Crush Resistance” that requires that the roof is of sufficient strength to withstand a load of 1.5 times the vehicle weight with less than 5 inches of deformation.
New standards have been proposed that require roof crush resistance of 2.5 times the unloaded vehicle weight. The new standards are being promulgated in an effort to further increase occupant protection. To meet or exceed the proposed standards with conventional roof construction techniques, considerably thicker and heavier sheet metal parts and reinforcements would be required. The increased part weight would adversely impact vehicle fuel economy. The use of larger parts and reinforcements tend to limit design freedom due to the need to provide more massive pillar designs.
The structure and strength of vehicle A-pillars, B-pillars and roof rails are key to satisfying the proposed new standards. The A-pillar/roof rail structure determines the initial resistance of the roof to crush loads. The B-pillar/roof rail structure is a key to meeting the peak load test specified in the new proposed standards. While the individual strength of the A-pillars, B-pillars and roof rails are a factor in roof crush resistance, strengthening these parts does not guarantee a strong roof structure. The strength of the joints between the A-pillars, B-pillars and roof rails is a major factor contributing to roof strength. The stiffness of the pillar/roof rail joints is also important in limiting joint deformation and increasing overall roof strength. Joint stiffness is also a factor in determining the static and dynamic stiffness of the vehicle body. Joint stiffness also affects noise, vibration and harshness (NVH) performance.
These and other problems associated with prior art vehicle roof support structures are addressed by applicants' invention as summarized below.